How to update TextView based on response from server inside RecyclerView adapter after user interaction?

Issue

I am trying to establish whether the user liked post or not by reading the response from server, assign value to boolean accordingly inside Retrofit.call.enqueue() and change UI's TextView value to +1 if true. How can I hold value of variable inside multiple callbacks and update UI based on it after call finishes?

In the UI I have two buttons(like\dislike) in RecyclerView adapter that updates data to MySQL Database after click and I am trying to update number of likes or dislikes after users interaction (+1 if user did not voted already, which I check via Retrofit call).

I have tried to assign value to global variable in Adapter class but the code runs before call is finished (I assume it's because Retrofit runs in separate thread by default). I have also tried to update UI in AsyncTask in onPostExecute() method like this:

private class LoadDataAsyncTask extends AsyncTask<String, Void, Boolean> {

        //variable to be updated based on response
        boolean voted = true;

        public LoadDataAsyncTask() {
            //todo
        }

        @Override
        protected Boolean doInBackground(String... params) {

            Log.v("Voted state start", String.valueOf(voted));
            GetUserVotes mApiGetUserVotes;
            mApiGetUserVotes = ApiUtils.getAPIServiceUserVotes();
            mApiGetUserVotes.getVotes().enqueue(new Callback<ResultVotes>() {
                    @Override
                    public void onResponse(Call<ResultVotes> call, Response<ResultVotes> response) {
                        if(response.body().getSuccess()==1)
                            voted = true;
                        else
                            voted = false;
                        if(!voted){
                            //todo
                        } else {
                            Log.v("Voted", String.valueOf(voted));
                            //todo
                        }
                    }

                    @Override
                    public void onFailure(Call<ResultVotes> call, Throwable t) {

                    }
                });
            Log.v("Voted state end", String.valueOf(voted));
            return voted;
        }

        @Override
        protected void onPostExecute(Boolean result) {
            Log.v("Voted state", String.valueOf(result));
            if(result) {
                //todo

            } else {
                //update UI TextView to +1 vote
                Log.v("onPostExecution", "Triggered");
            }
        }

    }

And results are:

1. V/Voted state start: false
2. V/Voted state end: false
3. V/Voted state: false
4. V/onPostExecution: Triggered
5. V/Voted: true

and should look like (if voted):

1. false
2. true
3. true
4. Triggered
5. true

I have also tried to make Interface like this:

public interface ResponseListener {

    void onSuccess();

    void onFail();
}

And to implement it in Adapter class (onFail() if not voted):

 @Override
    public void onBindViewHolder(final NewsViewHolder holder, int position) {

        final int iLikes = list.get(position).getPositiveVotes();
        final int iDislikes = list.get(position).getNegativeVotes();
        final ResponseListener retrofitResponseListener = new ResponseListener() {
            @Override
            public void onSuccess() {

            }

            @Override
            public void onFail() {
                int x = iNegativeVotes + 1;
                holder.textViewDislike.setText(String.valueOf(x));
            }
        };

    }

Here is code snippet:

 @Override
    public void onBindViewHolder(final NewsViewHolder holder, int position) {

        final int iLikes = list.get(position).getPositiveVotes();
        final int iDislikes = list.get(position).getNegativeVotes();

        holder.btnPositive.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                final boolean[] voted = {false};
                GetUserVotes mApiGetUserVotes;
                mApiGetUserVotes = ApiUtils.getAPIServiceUserVotes();
                mApiGetUserVotes.getVotes(email, url).enqueue(new Callback<ResultVotes>() {
                    @Override
                    public void onResponse(Call<ResultVotes> call, Response<ResultVotes> response) {
                        if(response.body().getSuccess()==1){
                            voted[0] = true;
                        }else{ voted[0] = false; }
                        if(!voted[0]){
                            //this is not working
                            holder.textViewDislike.setText(String.valueOf(x));
                        } else {
                            //do not update TextView
                        }
                    }

                    @Override
                    public void onFailure(Call<ResultVotes> call, Throwable t) {

                    }
                });
            }
        });
    }

How can I update TextView values after button click based on Retrofit response?

I have heard that there is something called 'Callback hell', what is it and how to effectively avoid it?

Solution

You do not need any global variable neither callbacks.

Just declared a public methods in your adapter that simply update your adapter list. You just need the position of updated item.

Update Likes:

public void updateLikes(int pos){
   int iLikes = list.get(position).getPositiveVotes();
   iLikes++;
   list.get(position).setPositiveVotes(iLikes);
   notifyDataSetChanged();  // very important 

}

Update Dislikes:

public void updateDislikes(int pos){
   int iDislikes = list.get(position).getNegativeVotes();
   iDislikes ++;
   list.get(position).setNegativeVotes(iDislikes);
   notifyDataSetChanged();  // very important 

}

And on your retrofit or Aysn success call simply call these methods:

adapter.updateLikes(position) or adapter.updateDislikes(position)

Answered By - Muazzam A.